Act 1:
In Governor Riccardo Warwick’s council chamber, the people’s representatives prepare to petition him. Some sing his praises, others, led by the conspirators Tom and Samuel, dwell on their grievances against him. Oscar the page hands Riccardo the guest list for the next masked ball. Riccardo is disturbed to discover the name of Amelia, the wife of his friend and advisor, Renato. The latter arrives and informs Riccardo of the existence of a plot against him. Riccardo, however, refuses to hear the names of the conspirators: he believes that the love of his people will protect him. The Chief Judge demands exile for the witch Ulrica whom he believes guilty of commerce with Satan. Oscar takes up her defence and an intrigued Riccardo decides to see for himself. Despite Renato’s appeal for caution, he sets off to visit Ulrica, inviting all present to accompany him. Ulrica is invoking the Prince of Darkness when Riccardo, disguised as a fisherman, enters. For Silvano, a sailor, she predicts wealth and success. Riccardo discreetly slips an officer’s certificate into the young man’s pocket. The latter sings Ulrica’s praises with the people. Amelia’s servant requests a secret consultation for his mistress. Everyone leaves except for Riccardo who conceals himself. Amelia asks the prophetess to help her eradicate the guilty love in her heart. Ulrica advises Amelia to gather a herb that only grows at the foot of the gallows. Riccardo swears to follow her to the bleak location. Oscar and his companions enter. Riccardo slips amongst them and asks Ulrica to tell him his future. She refuses to reply. On Riccardo’s insistence, she finally tells him that he is soon to die: murdered by the first person to shake his hand. Riccardo extends his hand to everyone around him but all shrink away. Renato arrives and grasps Riccardo’s hand. Riccardo scoffs at the prediction: how could his best friend wish him any harm?

Act 2:
At midnight, Amelia arrives at the place indicated by Ulrica. As she begs heaven’s help, Riccardo arrives and reveals his love. In her torment, Amelia declares her mutual love. However their duet is interrupted by the arrival of Renato who has come to warn Riccardo that the conspirators will attempt to kill him that very night. Amelia has just the time to hide behind her veil. Renato urges his friend to flee. The latter makes him promise to escort his veiled companion to the city gates without looking at her. Renato promises but the conspirators’ arrival prevents him from keeping his pledge. The conspirators demand to see the face of the veiled lady accompanying the governor. Renato is appalled to discover his wife. Angered as much by his friend’s betrayal and his wife’s infidelity as by the conspirators’ taunts, he summons Samuel and Tom to his home the following day.

Act 3
Renato wants to kill Amelia to avenge his dishonour. She begs Renato to allow her to kiss her son one last time. Renato relents and Amelia leaves. Remaining alone, Renato expresses his fury against Riccardo. Samuel and Tom arrive. Each demands the right to kill Riccardo. Renato suggests they draw lots. Amelia, who comes to announce Oscar’s arrival, is forced to draw the ticket naming the killer: it is to be Renato. Oscar invites Renato and his wife to the masked ball that very evening. Amelia searches for a way to warn Riccardo without betraying her husband. Riccardo writes an edict sending Renato and Amelia abroad. It is the only way he can renounce the young woman. Oscar hands him a note brought by a masked woman. The message warns him of imminent danger. Riccardo, refusing to be taken for a coward, prepares for the ball. At the ball Renato recognizes Oscar behind his mask and tries to discover Riccardo’s whereabouts, claiming he has important revelations for the governor. Oscar describes Riccardo’s costume. A masked Amelia approaches Riccardo and urges him to flee. Riccardo tells her of his decision to send her away and they bid each other a final farewell. Renato appears and stabs him. The horrified crowd tries to seize the assassin but the dying Riccardo orders that Renato be left in freedom. Before dying, he forgives his assassin.